Effect of TiO2 Nanotube Morphology on the Formation of Apatite Layer in Simulated Body Fluid

The objective of this work is to discuss the microstructural effect of TiO2 nanotubes on formation mechanism and morphology of apatite layer. An anodization method was employed to prepare self-organized TiO2 nanotubes on the surface of pure titanium, followed by these substrates being soaked in simulated body fluid (SBF) to form a bioactive layer. By manipulating the anodization time between 0.5 h and 3 h, nanotubes could be grown of any desired length ranging from 662 ± 5 nm to 1291 ± 5 nm. The diameter of rod-like apatite layer grown on the nanotubes decreased yet subsequently increased with the variation of nanotubular surface morphology and length. In addition, the nanotube length dependence of apatite formation can be ascribed to the different dissolution rate of nanotubes during the deposition of calcium phosphate (Ca-P) coatings, as well as the different penetration rate of Ca and P ions toward nanotube layer.